#include <stdio.h>
int main()
{int n;
int i=1;
int sum=0;
double t=0.0000;
double z=0.0000;
scanf("%d",&n);
while(i<=n)
{sum+=i;
t=1.0/sum;
z+=t;
i++;
}

printf("%.4f",z);


    return 0;
}
